'Hennissement' is derived from the verb 'hennir', attested in 1100 for human beings, and 30 years later for the "cry of a horse", in Philippe de Thaon's Bestiaire.
Moreover, 'hennir' is a borrowing[7][8] from the Latin 'hinnire'[7][8][9] which, as Quintilian notes in his Institutio Oratoria,[10] is formed on an onomatopoeia of the "horse cry":[7] the repetition of the vowel "i" evokes the sound of neighing.
[18] The horse's vocalizations have complex sounds, a wide bandwidth and varied frequencies, making them richer than those of most domestic animals.
The air expelled from the lungs pushes the lips away from the glottis, until the vocal cords return on themselves and momentarily close the respiratory tract, only to spread apart again, producing vibratory movements fast enough to give rise to sounds, much as happens when you blow into the reed of an oboe.
[19] The horse's throat, mouth and lips modify the nature of the sound emitted, while the power of the neigh is determined by the force with which air is expelled from the lungs.
[3] What's more, the animal emitting it generally adopts a very specific position, raising its head to clear its throat, which increases the power of the sound produced.
[28] The loudest squeak is also a threat: it indicates that the horse is about to express its anger physically, for example during a group feeding or when a mare pushes a stallion away.
[30] Films, especially westerns, frequently add recorded neighs to scenes with horses, which can give the false impression that the animal makes extensive use of this mode of communication.
A frequent theme in modern Greek folk songs is that of the woman who hears a horse neigh and recognizes the cry of her husband's mount, but not the man she has just spent the night with, whom she believes to be her lover.
In other songs, the neighing may be a decoy, a love code, an instrument of recognition to identify the horse rider, or a tribute from the equine to its departed master.
[31] In the Roman d'Alexandre, the fifteen-year-old future king passes the place where the terrible Bucephalus is confined one day and hears a loud neigh.
When he asks which animal it belongs to, one of his father's men replies that Bucephalus is locked up there because it feeds on human flesh, making it very dangerous.
When he hears Alexander's voice, Bucéphale lets out another neigh, this time very soft, and leans towards the young man he recognizes as his master.
According to the Tibetan hippologists who wrote the Touen-houang manuscripts (800-1035), a horse neigh sound comes from the wind, the force of life, from the base of its navel to its mouth.
[38] A bad horse is one that imitates the cry of a camel, vulture, cat, jackal, dog, crow, monkey or owl.
[39] Finally, Tibetan hippologists recommend not to draw omens from very young, very old, sick, hungry or thirsty horses,[38] but to pay close attention to neighing in all other cases.
In his Dictionnaire Infernal, Collin de Plancy speaks of Celtic hippomancy, thanks to the neighing and movement of white horses fed and kept in consecrated forests, considered to be the guardians of divine secrets.
[41] In his Morales sur le livre de Job, Pope Gregory I describes the horse as a true preacher, and its neigh as the voice of preaching.
[42] The myth of Balius and Xanthus, the horses of Achilles, one of which speaks and predicts the death of its master, provides some evidence of hippomancy through neighing.
[35] According to a legend recounted by Herodotus, the neighing of a horse plays a major role in the choice of government in ancient Persia.
As seven conspirators were unable to agree on the preferable form of government, it was decided that they would all ride to the same place the next morning before sunrise, and that whoever's horse was first to neigh in greeting to the sun would be made King of the Persians.
When Darius' horse arrives before sunrise, the smell and memory of the previous day's mare cause him to neigh with joy, and the kingdom falls to his master.
[43] In reality, Darius was probably chosen by consensus among the conspirators, but this legend illustrates the importance of the horse's neigh in defining the future king.